1. Field of the Invention
The present invention relates to an image display system which is capable of displaying an image on a screen in such a manner that the image can be observed only by a specific viewer or viewers and more particularly to such type of display system that can be made use of when it is necessary to convey image information to a particular person or persons in a public institution. The invention also relates to an image display method using such a system.
2. Description of the Related Art
Display systems represented by liquid crystal devices are known. In the case of such display systems, it is usual that the displayed images are watched by a plurality of viewers simultaneously.
However, where an image is displayed in a public institution for business or educational purposes, there is a case in which it is desired to convey selectively specific pieces of image information to specific viewers only but the conventional display systems can not serve such purposes.
Accordingly, an object of the present invention is to provide an image display system having a structure such that a plurality of images can be individually observed by a plurality of viewers, and also to provide an image display method using such a system.
According to a first aspect of the invention, the image display system is so constructed that a first image having a first state of polarization and a second image having a second state of polarization are projected with one image superimposed on another, wherein the first image is entirely white.
According to a second aspect of the invention, the image display system is so constructed that a first image having a first state of polarization and a second image having a second state of polarization are projected with one image superimposed on another, wherein the second image contains specific information to be displayed and the first image forms a white pattern to cover a specific part of or the whole of the second image.
According to a third aspect of the invention, the image display system is so constructed that a first image having a first state of polarization and a second image which is time-division displayed and has a second state of polarization are projected with one image superimposed on another, wherein the second image is intended to display specific information and the first image forms a white pattern to cover a specific-part of or the whole of the second image.
In any of the image display systems thus constructed, the first and second images may be circularly polarized with clockwise rotation and with counterclockwise rotation, respectively, or vice versa.
Alternatively, the first and second images may be linearly polarized with their planes of polarization intersecting at right angles with each other.
In another alternative approach, the first and second images are circularly polarized in opposite rotating directions, and their rotating directions are alternately reversed in successive time frames under the time-division display scheme. This approach enables a viewer to selectively observe the second image without being disturbed by the white pattern formed by the first image.
In one method of the invention for providing on-screen visual display, a first image having a first state of polarization and a second image having a second state of polarization are projected with one image superimposed on another, the first image being entirely white, wherein a viewer looking through an optical filter which selectively allows light of the second state of polarization to pass through can see the second image.
In another method of the invention for providing on-screen visual display, a first image having a first state of polarization and a second image having a second state of polarization are projected with one image superimposed on another, the first image forming a white pattern just to cover such part of the second image that should be hidden from view of unspecified viewers, wherein a viewer looking through an optical filter which selectively allows light of the second state of polarization to pass through can see the second image.
According to a fourth aspect of the invention, the image display system for projecting a plurality of images on a screen with one image superimposed on another comprises a first liquid crystal projector for alternately projecting mutually differing first and second images having a first state of polarization in successive time frames in accordance with a time-division display scheme, a second liquid crystal projector for projecting a white image having a second state of polarization which differs from the first state of polarization, a first viewing device assigned to a first viewer incorporating a first liquid crystal shutter which opens and closes in synchronism with time-division display operation of the first liquid crystal projector to selectively allow the first image to pass through and a first optical filter which allows the image having the first state of polarization to pass through, and a second viewing device assigned to a second viewer incorporating a second liquid crystal shutter which opens and closes in synchronism with the time-division display operation of the first liquid crystal projector to selectively allow the second image to pass through and a second optical filter which allows the image having the first state of polarization to pass through, whereby the first viewer wearing the first viewing device can selectively see the first image and the second viewer wearing the second viewing device can selectively see the second image, while viewers not wearing such a viewing device can only see the white image.
According to a fifth aspect of the invention, the image display system for projecting a plurality of images on a screen with one image superimposed on another comprises a first liquid crystal projector for alternately projecting images for right and left eyes in successive time frames in accordance with a time-division display scheme, the images having a first state of polarization, a second liquid crystal projector for projecting a white image having a second state of polarization which differs from the first state of polarization, and a viewing device assigned to a viewer incorporating a first liquid crystal shutter which, provided at the right-eye side of the viewing device, opens and closes in synchronism with time-division display operation of the first liquid crystal projector to selectively allow the image for the right eye to pass through, a second liquid crystal shutter which, provided at the left-eye side of the viewing device, opens and closes in synchronism with the time-division display operation of the first liquid crystal projector to selectively allow the image for the left eye to pass through, a first optical filter which, provided at the right-eye side of the viewing device, allows the image having the first state of polarization to pass through, and a second optical filter which, provided at the left-eye side of the viewing device, allows the image having the first state of polarization to pass through, whereby the viewer wearing the viewing device can selectively see a three-dimensional image, while viewers not wearing such a viewing device can only see the white image.
According to a sixth aspect of the invention, the image display system comprises a liquid crystal panel including a plurality of active matrix regions and common peripheral circuits for controlling horizontal and/or vertical scanning operation in the active matrix regions, the active matrix regions and the peripheral circuits being formed on a single substrate, a polarizer for giving a first state of polarization to at least one of images generated by the active matrix regions, a polarizer for giving a second state of polarization to an image other than the images to which the first state of polarization is given, and a projector for projecting the images generated in the active matrix regions of the liquid crystal panel on a screen with one image superimposed on another, wherein at least one of the images generated by the active matrix regions is entirely white.
According to a seventh aspect of the invention, the image display system comprises a liquid crystal panel including a plurality of active matrix regions and common peripheral circuits for controlling horizontal and/or vertical scanning operation in the active matrix regions, the active matrix regions and the peripheral circuits being formed on a single substrate, a polarizer for giving a first state of polarization to at least one of images generated by the active matrix regions, a polarizer for giving a second state of polarization to an image other than the images to which the first state of polarization is given, and a projector for projecting the images generated in the active matrix regions of the liquid crystal panel on a screen with one image superimposed on another, wherein at least one of the images generated by the active matrix regions forms a white pattern just to cover such part of the other images that should be hidden from view.
In either of the image display systems comprising the aforementioned liquid crystal panel, the first and second states of polarization may be circular polarization with opposite rotating directions, or linear polarization with their planes of polarization intersecting at right angles to each other.
In one preferred embodiment, the first and second liquid crystal projectors project respective images on a common screen. The image projected by the second liquid crystal projector is circularly polarized with clockwise rotation as the image passes through a polarizing plate and a quarter-wave plate. On the other hand, the image projected by the first liquid crystal projector is circularly polarized with counterclockwise rotation as the image passes through a polarizing plate, a xcfx80-cell employing a liquid crystal cell for rotating the plane of polarization by 90 degrees and a quarter-wave plate.
The clockwise-rotating, circularly polarized image An projected by the second liquid crystal projector and the counterclockwise-rotating, circularly polarized image Bn projected by the first liquid crystal projector are therefore superimposed on the same screen.
In this embodiment, the image An projected by the second liquid crystal projector is blank, or entirely white, while the image Bn projected by the first liquid crystal projector contains specific visual information.
When viewed with the naked eye, a combination of the white image An and the image Bn containing the specific visual information projected on the screen appears totally white. This is because the image Bn is masked by the white image An.
Any viewer who wished to see, or need to see, the visual information contained in the image Bn should wear a dedicated viewing device equipped with an optical filter which selectively allows counterclockwise-rotating, circularly polarized light emitted by the first liquid crystal projector to pass through and look at the screen from the opposite side of the projectors. (It is to be noted that the rotating direction of the circularly polarized light is apparently reversed when viewed from the opposite side of the projectors.)
With this arrangement, it is possible to completely hide away the image Bn from view of those people who are not willing to see, or need not see, the image Bn, just allowing specific viewers to see it. The embodiment may be modified such that the image An forms a particular white pattern to mask a specific part of the image Bn. This makes it possible to hide specific pieces of visual information from public view.
The arrangement of the invention can be used for conveying visual information to concerned personnel only through a video screen which can be seen by the general public. Potential applications of this kind would be found in various industrial fields including the use in public spaces and buildings.
The invention also makes it possible to present a three-dimensional image to specific viewers by using a time-division display technique.
According to the invention, each image display system employs an integrated liquid crystal panel to produce individual images. The use of such integrated liquid crystal panels serves to offer such advantages as compact design, improved productivity and higher reliability of the image display systems.